Single optical fiber connector

ABSTRACT

A hermaphroditic connector for coupling a pair of single optical fibers is disclosed. The connector comprises a pair of connector members each containing at least one single optical fiber terminated by a termination pin. The pin includes a metal eyelet crimped about the optical fiber in three places providing three, spaced, curved indentations which centrally position the fiber in the pin. When the connector members are mated, the mating termination pins are positioned so that the indentations therein are generally aligned. A cam or spring device is forced into the indentations in the mating termination pins to accurately laterally align the pins and, hence, the optical fibers therein.

CROSS REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 682,274, filed May 3, 1976now U.S. Pat. No. 4,088,390 which is a continuation-in-part of Ser. No.629,004 filed Nov. 5, 1975, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates generally to a connector and, morespecifically, to an optical coupler for single fiber optic cables.

The employment of fiber optic cables or light guides, also sometimesreferred to as optical communication fibers, for the transmission ofinformation-bearing light signals, is now an established art. Muchdevelopment work has been devoted to the provision of practical low-lossglass materials and production techniques for producing glass fibercables with protective outer claddings or jackets. The jackets make themresemble ordinary metallic-core electrical cable upon superficialexternal inspection. Obviously, if fiber optic cables are to be used inpractical signal transmission and processing systems, practicalconnectors for the connection and disconnection of fiber optic cablesmust be provided.

Some references will now be given for background in the state of fiberoptic art in general. An article entitled, "Fiber Optics", by NarinderS. Kapany, published in Scientific American, Vol. 203, pgs. 72-81,November 1960, provides a useful background in respect to sometheoretical and practical aspects of fiber optic transmission.

Of considerable relevance to the problem of developing practical fiberoptic connectors, is the question of transfer efficiency at theconnector. Various factors, including separation at the point ofabutment, and lateral separation or axial misalignment, are among thefactors effecting the light transfer efficiency at a connector. In thisconnection, attention is directed to the Bell System Technical Journal,Vol. 50, No. 10, December 1971, specifically to an article by D. L.Bisbee, entitled, "Measurement of Loss Due to Offset, and EndSeparations of Optical Fibers". Another Bell System Technical Journalarticle of interest appeared in Vol. 52, No. 8, October 1973, and wasentitled, "Effect of Misalignments on Coupling Efficiency on Single-ModeOptical Fiber But Joints", by J. S. Cook, W. L. Mammel and R. J. Grow.

Fiber optic bundles are normally utilized for only short transmissiondistances in fiber optic communications networks. On the other hand,fibers are used individually as optical data channels to allowtransmission over many kilometers. At present, most fiber optic cablesare multi-fiber bundles due to the less stringent splicing requirements,greater inherent redundancy and higher signal-to-noise ratio. Thedifficulty in achieving connections between single fibers which areinsensitive to axial misalignment problems has created an obstacle tothe use of long run single data transmission systems.

Therefore, a connector or coupler is required to eliminate lateraltolerances if low-loss connections are to be obtained in the use ofsingle fiber optical transmission arrangements. "V" groove and metalsleeve arrangements have been used to interconnect single fibers.Reference is made to U.S. Pat. No. 3,768,146 which discloses a metalsleeve interconnection for single fibers.

Another known device, as shown in U.S. Pat. No. 3,734,594, utilizes adeformable annular core having pressure plates at the ends. The fiberends are inserted into the core and an axial force is applied to theplates to deform the core radially, thereby aligning and securing thefibers.

The prior devices, however, do not readily provide sufficient accuracyfor joining and aligning small diameter cores of optical fibers.

Copending application of Charles K. Kao entitled, "Precision OpticalFiber Connector", Ser. No. 613,390, filed Sept. 15, 1975, assigned tothe assignee of the present application, discloses a single opticalfiber connector in which the ends of mating fibers are precisely alignedand coupled together in the interstice between three like contactingcylindrical rods. The rods are mounted along and around the fiberswithin an adjustable connector assembly. Means is provided for expandingthe interstice to insert the fiber ends and for clamping the rods inposition around the fibers. Copending application of Charles K. Kaoentitled, "Precision Surface Optical Fiber", Serial No. (Kao 17), filedconcurrently herewith, assigned to the assignee of the presentapplication, discloses an optical fiber in which the plastic claddingthereof is formed with three rounded indentations along its surface anda thin metal ferrule is formed around the cladding at the mating end ofthe fiber. A pair of such fibers may be aligned in a three rodarrangement to the type mentioned above.

The purpose of the present invention is to provide a separable connectorassembly which will provide a controlled accurate alignment of matingoptical fiber termination pins in a manner which minimizes lighttransmission losses, and is practical for commercial field use.

SUMMARY OF THE INVENTION

According to the principal aspect of the present invention, there isprovided a fiber optic connector for coupling a pair of single opticalfibers. The connector comprises a pair of mating connector members eachcontaining at least one single optical fiber terminated by a terminationpin. The pins are axially aligned with each other when the connectormembers are mated. Each termination pin includes an eyelet surroundingits respective optical fiber. Each eyelet has a mating end face adaptedto abut the end face of the eyelet of the mating aligned terminationpin. The wall of the eyelet adjacent to the end face embodies threecircumferentially spaced indentations each disposed in juxtaposition tothe fiber. Means are provided on the connector members for locating thetermination pins so that the indentations in the eyelets are generallyaligned when the connector members are mated thereby providing threepairs of aligned indentations. Means are also provided for effectingaccurate lateral alignment between the eyelets when the connectormembers are mated. Such alignment means extends to opposite sides of thepoint of abutment of the eyelets and embodies three elements each ofwhich extends into one pair of aligned indentations in the eyelets toalign the eyelets. The alignment means may be spring elements which biasthe indentations inwardly toward the fibers in the eyelets.Alternatively, the alignment means comprises two stationary edges whichextend into two pairs of aligned indentations in the mating eyelets anda movable cam follower which is forced into the third pair of alignedindentations when the connector members are mated, thereby providing apositive force acting upon all three pairs of aligned indentations inthe eyelets of the mating termination pins. The application of suchforce on the indentations brings the indentations in extremely closeproximity to the fibers. Since the point of alignment of the matingeyelets is the bottoms of the indentations which are closely adjacent tothe fibers, very precise lateral alignment of the fibers is achieved.Preferably, the connector members are identical so that the connectorassembly is hermaphroditic which simplifies field use and servicing ofthe connector.

Other aspects and advantages of the invention will become more apparentfrom the following description taken in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of the connector of the presentinvention in which the mating connector members of the connector areinterengaged;

FIG. 1a is a partially exploded perspective view of the internalcomponents of the connector members illustrated in FIG. 1;

FIG. 2 is a longitudinal sectional view taken along line 2--2 of FIG. 3through one of the termination pins employed in the connector of thepresent invention;

FIG. 3 is a front end view of the termination pin illustrated in FIG. 2;

FIG. 4 is an enlarged end view of the crimped eyelet employed in thetermination pin illustrated in FIGS. 2 and 3;

FIG. 5 is a side elevational view of the eyelet before it is crimped tothe optical fiber in the termination pin;

FIG. 6 is a front end view of the eyelet illustrated in FIG. 5;

FIG. 7 is a transverse sectional view through a crimp tool utilized forcrimping the eyelet to the optical fiber mounted in the termination pinillustrated in FIGS. 2 to 4;

FIG. 7a is an enlarged fragmentary sectional view similar to FIG. 7showing the crimp tool in its actuated position;

FIG. 8 is a front end view of one of the connector members of theconnector illustrated in FIG. 1 with the termination pins being shownonly in the upper half of the connector body;

FIG. 9 is a longitudinal sectional view taken along line 9--9 of FIG. 8with all the termination pins removed from the connector body;

FIG. 10 is a longitudinal sectional view similar to FIG. 9 but showingthe front ends of the internal components of the mating connectingmembers fully engaged with the mating termination pins in abuttingengagement;

FIG. 11 is an exploded perspective view of a pair of termination pinsand a spring alignment device therefor in accordance with an alternativeembodiment of the invention; and

FIG. 12 is a transverse sectional view through the spring alignmentdevice illustrated in FIG. 11 with the termination pins mounted thereinin axial alignment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is generally applicable to the interconnection ofa pair of single optical fibers. The invention will be describedspecifically as utilizing optical fibers having a plastic cladding, suchas TPE clad silica. It will be appreciated, however, that the connectorof the present invention may be utilized to couple other forms of singleoptical fibers, with or without plastic claddings or jackets. Theinvention, therefore, has universal application for the coupling ofsingle optical fibers.

Referring now to FIG. 1 of the drawings in detail, there is illustratedthe connector of the present invention, generally designated 10. Inaccordance with one feature of the invention, the connector 10 ishermaphroditic, and comprises identical mating connector members 12a and12b. The connector members 12a and 12b terminate fiber optic cables 14aand 14b, respectively. Since the connector members 12a and 12b areidentical, the same reference numerals will be utilized to designateidentical parts therein. Each connector member includes a generallycylindrical shell 16 and a coupling ring 18. Each coupling ring 18 ismounted for rotation on its respective shell 16, but is prevented fromaxial movement thereon by means of a retaining ring 20. Each couplingring embodies a plurality of circumferentially spaced, forwardlyextending arms 22 formed with inwardly extending pins 24 at the ends ofthe arms. The arms are equally spaced from each other. A bayonet slots26 are formed in each coupling ring 18 intermediate the arms 22. Theslots open at the forward face 28 of the coupling ring. In order tocouple the connector members 12a and 12b together, the coupling rings 18are positioned so that the respective pins 24 on the arms 22 engage inthe bayonet slots 26 so that when the rings are rotated in a clockwisedirection, the shells 16 of the respective connector members will bedrawn axially toward each other into full mating interengagement. Whilea hermaphroditic bayonet coupling arrangement has been disclosed herein,it will be appreciated that other forms of hermaphroditic couplingdevices may be utilized for interconnecting the connecting members 12aand 12b.

Reference is now made to FIG. 1a of the drawings which illustrates thecomponent parts of the mating connector members 12a and 12b. The partsof each connector member include basically a cylindrical support body30, a fiber spreader device 32, and an externally threaded retainingring 34. The support body has an outwardly extending annular flange 36defining a forwardly facing annular shoulder 38. When the support body30 is mounted in its respective connector shell 16, the shoulder 38engages a rearwardly facing shoulder (not shown) on the interior of theshell. The spreader device 32 is mounted behind the support body 30 andis retained in the shell by the retaining ring 34, which is threadedinto the rear of the shell. The specific construction of the supportbody 30 and spreader device 32 will be described in greater detaillater.

The fiber optic cables 14a and 14b each comprises a central strengthmember 40 and a plurality of single optical fibers 42 disposed aroundthe cylindrical surface of the strength member. Preferably, the fibersare plastic clad silica. However, other forms of fibers may be utilizedas explained hereinbefore. Six of such fibers are incorporated in thecable disclosed herein. It will be understood that the cable may employany number of fibers so long as there is room in the support body formounting the termination pins for the fibers. Such pins are generallydesignated 44.

Reference is now made to FIGS. 2 to 4 of the drawings which illustratein detail the structure of a termination pin 44. The termination pincomprises an elongated, generally cylindrical, plastic ferrule 46 havinga central longitudinally extending passage 48 therethrough. An opticalfiber 42 is mounted through the passage and is retained therein by asuitable epoxy or cement 50. The ferrule 46 is formed with alongitudinally extending key 52 and an annular groove 54 in front of thekey which receives an O-ring 56, as seen in FIG. 1a.

The termination pin 44 has a forward flat face 56 (see FIG. 3). A hub 58extends forwardly from the face 56 coaxial with the longitudinal axis ofthe passage 48 and terminates in an end face 60. A bore 62 in the hubextends from the end face 60 rearwardly to the passage 48. The bore hasa smaller diameter than the passage and is dimensioned to slidablyreceive the fiber 40 therethrough. Three cylindrical posts 64 extendforwardly from the forward face 56 of the ferrule 46. The posts arespaced from the hub 58 and are equally spaced circumferentially aboutthe forward face 56. That is, the centers of the posts are offset fromeach other 120°. The posts have flat forward ends 66 which lie in acommon plane transverse to the axis of the ferrule 46 and forward of theend face 60 of the hub 58.

A metal eyelet 68 is mounted on the hub 58 of the plastic ferrule 46.The eyelet is shown in FIGS. 5 and 6. It comprises a hollow metal sleevehaving a rear, relatively large end 70 and a smaller forward end 72. Therear end 70 is dimensioned to fit over the hub 58 with an interferencefit so that it will be firmly retained on the plastic ferrule. Thesmaller forward section 72 of the eyelet extends forwardly from the endface 60 of the hub and forward edge 74 of the eyelet is coplanar withthe flat forward ends 66 of the posts 64.

The fiber 42 extends to the forward edge 74 of the eyelet. The fiber hasa light transmitting core or light guide 76 and a plastic cladding 78.The forward end 72 of the metal eyelet is crimped to provide threecircumferentially spaced indentations 80 and three radially outwardlyextending ribs 82 as best seen in FIG. 4. The ribs and the bottoms ofthe indentations are spaced 120° apart. The indentations 80 haveidentical circular configurations. The wall of the eyelet is crimped sothat the indentations are closely adjacent to the core 76 of the fiber,but not quite touching the core. If the eyelet were crimped to such anextent that the wall of the eyelet touched the core, the core may becomecrushed. The plastic cladding 78 of the optical fiber extrudes outwardlyduring the crimping operation to substantially completely fill the openspace in the end of the eyelet. The indentations 80 accurately centrallylocate the core 76 of the optical fiber in the eyelet and providelocating points close to the core so as to permit accurate alignment ofthe cores of optical fibers in mating eyelets in the connector members12a and 12b.

The posts 64 on the plastic ferrule 46 are positioned in radialalignment outwardly from the ribs 82 of the eyelet, as seen in FIG. 3,and thus out of radial alignment with the indentations 80 in the eyelet.The posts 64 provide an enlarged abutting contact area between matingtermination pins so that less pressure exists between the end faces ofthe eyelets 68, which might cause scratches on the faces of the corestherein, thereby producing light transmission losses.

The end of the termination pin 44 is polished to a flat surface. Sincethe plastic cladding 78 and fiber core 76 are softer than the metaleyelet 68, the mating end face 90 of the clad fiber becomes slightlydished during the polishing operation, as seen in FIG. 2, so that theend face of the fiber core is positioned slightly behind the forwardface of the termination pin. As a consequence, when two mating pins areabutted, the cores 76 will not quite touch.

Reference is now made to FIG. 7 of the drawings which illustrate intransverse section a crimp tool for forming the indentations 80 of theeyelet 68. The tool is generally designated 92. The tool comprises aninner cylindrical body 94 surrounded by an outer ring 96, which isrotatable with respect to the body 94. Three radially extending slots 98are formed in the body 94 offset from each other 120°. Each slot carriesa crimp jaw 100. The inner end of each jaw is formed with a narrow rib102 having an inner arcuate surface 104. A termination pin 44 is shownpositioned in a center bore 105 in the body 94. It is noted thatsufficient space is provided between the adjacent posts 64 on thetermination pin so that the ribs 102 on the jaws may pass therethroughwhen the jaws are shifted radially inwardly in the slots 98. The outerends 106 of the jaws are rounded and engage arcuate cam surfaces 108 onthe ring 96. When the ring is rotated counterclockwise relative to thebody 94, the jaws 100 are forced radially inwardly to the positionindicated in dotted lines at 110 so that the arcuate inner surfaces 104of the jaws will deform the eyelet 68 to form the indentations 80. Itwill be appreciated that the posts 64 on the ferrule 46 may have aconfiguration other than cylindrical (which is preferred for simplicityin the molding of plastic parts) just so the posts will not interferwith the movement of the jaws 100 in the tool 92 to crimp the eyelet 68.For example, the posts 64 may have a triangular or trapezoidalcross-section, if desired.

The fiber spreader device 32 has a generally circular forward base 114adjacent to the cylindrical support body 30 and a rearwardly extendingconical section 116 terminating in an apex 116. Six arcuatelongitudinally extending grooves 120 are formed in the outer surface ofthe base 114 and the conical section 116 of the spreader device. Thegrooves are equally spaced circumferentially about the spreader deviceand are dimensioned to slidably receive the optical fibers 42 of thefiber optical cable. A longitudinally extending passage 122 extends fromthe front face of the spreader device 32 rearwardly to the apex 118coaxial with the circular base 114. The passage 122 receives the centralstrength member 40 of the fiber optic cable. Circular recesses 124 areformed in the outer surface of the circular base 114 of the spreaderdevice in alignment with the grooves 120. The termination pins 44connected to the fibers 42 of the fiber optic cable are positioned inthe recesses 124 with the keys 52 of the pins located in keyways 126 inthe recesses for locating the indentations 80 in the eyelets 68 of themating pins in general alignment when the connector members 12a and 12bare interengaged. Outwardly extending arcuate flanges 128 are formed onthe circular base 114 adjacent to its forward face. A termination pinretainer ring, generally designated 129, is mounted on the circular base114 of the spreader device 32. The ring comprises two half-ring sections130. Each half-ring section embodies three rearwardly extending grooves132 and forwardly extending recesses 134 complementary to the grooves120 and recesses 124 for positioning the termination pins 44 and opticalfibers 42 on the spreader. Each half-ring section 130 is formed with anarcuate groove 136 at its forward inner edge defining a forwardly facingshoulder 138 which engages the flanges 128 on the circular base 114 ofthe spreader. The outer diameter of the forward section 140 of theretainer ring 120 is approximately equal to the diameter of the rearflange 36 on support body 30 and the rear section 144 of the ring has asmaller diameter than the forward section defining therebetween arearwardly facing annular shoulder 146. The retaining ring 34 isdimensioned to slide over the rear section 144 of the retainer ring 129with its forward end 148 abutting the shoulder 146 on the ring 129.Thus, when the retaining ring 34 is threaded into the rear of the shell16 of its respective connector member, it exerts a forwardly directedaxial force on the shoulder 146. Since the shoulders 138 on the forwardinner edges of the half-ring sections 130 engage the flanges 128 on thespreader device 32, the device is pressed up against the rear face 150of the support body 30 in the shell.

The support body contains a circular array of six longitudinal bores 152which extend from the rear face 150 of the support body to the forwardface 154 thereof. The bores are circumferentially spaced apart 60° fromeach other in support body and are in alignment with the circular recess124 in the spreader device 32. The bores are dimensioned to slidablyreceive the termination pins 44. Each bore 152 has a recess orcounterbore 154' opening at the rear face 150 of the support body. Whenthe spreader device 32 is pressed up against the rear face 150 of thesupport body by the retaining ring 34, the forward faces of the ring 129and the circular base 114 of the spreader device, and the bottoms 156 ofthe counterbores 154' form therebetween annular grooves which areaxially aligned with the grooves 54 in the termination pins. As seen inFIG. 1A, the diameter of each O-ring 56 is sufficiently great that thering extends outwardly beyond the surface of the pin 44 into the groovein the connector body surrounding groove 53. The O-ring is loose in thealigned grooves. The area of the front faces of the ring 129 and base114 adjacent each counterbore or groove 154' provides a forwardly facingannular shoulder behind the O-ring. The forward wall of the groove 54 ineach termination pin provides a rearwardly facing annular shoulder. Whenthe connector members 12a and 12b are mated, the mating end faces of thetermination pins axially abut and the O-rings 56 become compressivelyengaged between the aforementioned shoulders providing a resilient forcetending to resist axial rearward movement of the pins in theirrespective connector bodies. The O-rings provide for axial tolerancerelief of the mating end faces of the termination pins and also exert aforwardly directed spring force upon the pins to assure that the matingend faces of the termination pins in the respective connector members12a and 12b will abut with a slight axial force therebetween. Thus, thisarrangement functions in a similar fashion to the axial tolerance reliefinvention disclosed in my copending application entitled, "Fiber OpticConnector with Axial Tolerance Relief", Ser. No. 597,943, filed July 21,1975, now U.S. Pat. No. 3,947,182. However, the present arrangement issimpler in construction and requires fewer parts, although it does notpermit individual removal of the termination pins from the connectorunless the components are disassembled, as illustrated in FIG. 1A.

As seen in FIGS. 1A, 8, and 9, a semi-cylindrical plate 160 is removablymounted on one-half of the circular forward face 154 of the support body30. The diameter of the semi-cylindrical plate 160 is slightly less thanthe diameter of the forward part of the support body 30 so that theouter cylindrical surface 162 of the plate is spaced inwardly a shortdistance from the cylindrical surface of the support body, as best seenin FIG. 1. The inner flat surface 164 of the plate 160 is closelyadjacent to a longitudinal plane passing through the center axis of thesupport body 30. A pair of locating pins 165 extend rearwardly from therear face 166 of the plate 160. The pins extend into two bores 167 inthe forward face of the support body 30 for positioning the plate on thebody in the manner just described.

A centrally located semi-cylindrical recess 168 is formed in the innersurface 164 of the plate 160. A flange 170 is formed adjacent to therear face 168 of the plate 160 and extends over a central threadedpassage 172 in the support body 30. A screw 174 extends through a hole176 in the flange 168 and is threaded into the bore 172 to removablysecure the plate 160 on the forward face of the support body.

The plate 160 contains three longitudinal extending passages, 180extending from the rear face 166 to the front face 182 of the plate. Thepassages are aligned with the three bores 152 in the support body 30underlying the plate 160. The forward ends of the termination pins insuch bores 152 extend forwardly from the forward face 154 of the supportbody into the passages 180, with the mating end faces of the pinsterminating intermediate the front face 182 and rear face 166 of theplate 160. Thus, the termination pins in the plate 160 are shrouded andprotected from damage. The three termination pins in the bores 152 inthe other half of the support body 30 extend outwardly from the forwardface 154 thereof the same distance as do the termination pins thatextend into the passages 180. When the connector members 12a and 12b arerotatably positioned relative to each other 180° out of phase (so thatthe semi-cylindrical plates 160 are out of alignment), the exposedtermination pins in the one-half of each connector support body willslidably engage into the passages 180 in the semi-cylindrical plate 160on the other connector member support body to make a butting engagementtherewith intermediate the ends of the passages 180. Since the plates160 are mounted on their respective support bodies 30 by screws 174, theplates may be removed to permit cleaning of the end faces of theterminations pins 44. It will be appreciated that by the foregoingarrangement of the terminations pins, and the mounting of half of thepins in a removable semi-cylindrical plate, the two identical connectormembers of the present invention provide a hermaphroditic connectorassembly so that identical connector members may be attached to oppositeends of a fiber optic cable, and connection may be made at each end ofthe cable to a mating connector member without having to reverse thedirection of the cable.

It will be appreciated that due to tolerances in the various parts inthe connector assembly, the mating termination pins in the connectormembers are only generally axially aligned therein. The keys 52 on thetermination pins engaging the keyways 126 in the spreader device 132serve to generally rotationally align the termination pins so that theindentations 80 in the crimped eyelets 68 are longitudinally aligned inthe passages 180 in the plates 160. An important feature of theinvention is the providing of means for accurately aligning theindentations in the mating eyelets so that the light transmitting fibercores therein will be axially aligned. Accurate alignment of the fibercores can be achieved since the alignment means of the present inventionlocates off the indentations in the eyelets, which are extremely closeto the fiber cores. It is desirable in order to achieve precise axialalignment of the fiber cores that not only accurate longitudinalalignment be achieved between the indentations in the eyelets of themating termination pins, but also that the indentations be compressedradially inwardly toward the cores. This is because after an eyelet isdeformed by the crimp tool 92, the metal of the deformed eyeletelastically recovers somewhat, leaving a greater than desired spacebetween the wall of the eyelet and the fiber core. Furthermore, thecrimping of the eyelet about the fiber core compresses the plasticcladding of the optical fiber. The compressed cladding exerts a force onthe crimped eyelet thereby forcing the indented walls of the eyeletradially outwardly. In the preferred embodiment of the invention, toachieve precise alignment of the mating fiber cores, cam followers 190are mounted in the passages 180 in removable plate 160. One cam followeris shown removed from its respective passage 180 in the connector member12b illustrated in FIG. 1a so that the position of the termination pin44 in the passage may be clearly seen. Referring to FIGS. 8 and 9, it isnoted that each passage 180 in plate 160 extends radially outwardly andopens at the outer cylindrical surface 162 of the plate. The oppositesides of the passage are formed with longitudinally extending inwardlyfacing shoulders 192. The cam follower 190 is formed with longitudinallyextending outwardly facing shoulders 194 which engage the shoulders 192and thereby prevent removal of the cam followers 190 radially from thepassages 180. The cam followers are mounted longitudinally into thepassages from the front face 182 of the plate 160.

The inner end 196 of the passage 180 is formed with a pair of spaced,curved longitudinally extending channels 198, which receive two of thecylindrical posts 64 of the termination pin 44. A radially inwardly,extending longitudinal slot 200 is located in the inner end 196 ofpassage 180 intermediate the curved channels 198. A longitudinallyextending bore 202 extends from the front face 182 to the rear face 166of the plate 160 radially inwardly from the slot 200. The third post 64of the termination pin 44 is slidably received in the bore 202. Roundededges 204 are provided between the sides of the slot 200 and the curvedchannels 198. The curvature of the edges 204 corresponds to thecurvature of the curved indentations 80 in the eyelet 68 on thetermination pin 44. The slot 200 is dimensioned to slidably receive oneof the ribs 82 of the eyelet. Thus, the edges 204 provides stationarytool for deforming two indentations 80 of the eyelet inwardly toward thefiber core therein when the eyelet is forced radially inwardly.

The inner end of the cam follower 190 is formed with a longitudinallyextending ridge 206 having an inner curved surface 208 of arcuate convexconfiguration complementary to the curvature of the indentation 80 ofthe eyelet 68. The ridge 206 is sufficiently narrow that it may passbetween the posts 64 of the termination pin lying in the channels 198.It is noted that the rounded edges 204 and the ridge 206 on the camfollower 90 extend to opposite end faces of the plate 180 and hence, onopposite sides of the point of abutment of the mating end faces of thetwo termination pins in the passage 180. It will be appreciated thatwhen a radially inwardly directed force is applied to the cam follower190, the ridge 206 on the inner end of the follower and the roundededges 204 on the bottom of the passage 180 in plate 160 will function ina similar manner as the jaws 110 in the crimp tool 92 illustrated inFIG. 7. That is, the cam follower and ridges 206 will apply positiveradially inwardly directed force upon the generally aligned indentations80 in the mating eyelets positioned in the passage 180 thereby locatingthe indentations in closer proximity to the fiber cores to overcome anyexpansion of the wall of the eyelets due to elastic recovery of themetal of the compression of the plastic cladding of the optical fiberafter original crimping of the eyelet by the tool 92. Since the locatingpoints for alignment of the mating eyelets are extremely close to thelight transmitting fiber cores therein, highly accurate, controlledaxial alignment of the cores is achieved by the present invention.

Any suitable means may be utilized for camming the cam followers 190radially inwardly in the passage 180 to achieve axial alignment of theoptical fibers in mating termination pins mounted. Preferably, suchmeans comprises a semi-cylindrical forwardly extending wall 210 on theforward face 154 of the support body 30 opposite to the plate 160. Thewall 210 and the inner surface 164 of the plate 160 define asemi-cylindrical recess 212 which is dimensioned to slidably receivethereinto the semi-cylindrical plate 160 on the mating connector member.The inner surface 214 of the wall 210 slides over the outer cylindricalsurface 162 of the mating connector member when the two connectormembers 12a and 12b are interengaged, and engages the outer curvedsurfaces 216 of the cam followers 190 which extend beyond the outercylindrical surface 162 of plate 160. Preferably, a chamfer 218 isformed on the inner surface 214 of the semi-cylindrical wall 210 and theforward outer surfaces of the cam followers 190 are chamfered asindicated at 220. The mating chamfered surfaces 218 and 220 facilitatethe sliding of the semi-cylindrical wall 210 on one connector memberover the outer surfaces of the cam followers 190 in the mating connectormember. Preferably, two longitudinally extending slots 222 are formed ineach wall 210 offset 60° from each other and from the side edges 224 ofthe wall, thereby providing three individual arcuate wall sections 226for independently engaging the three cam followers 190 on the matingconnector member.

Reference is made to FIG. 10 of the drawings which illustrates the frontends of the connector bodies of the two connector members 12a and 12bwhen the latter are fully interengaged by the coupling rings 18. FIG. 10clearly illustrates the hermaphroditic arrangement of the presentinvention which allows two identical connector members to be coupled toopposite ends of a fiber optic cable. In FIG. 10, the cam followers 190in the respective connector members are shown forced radially inwardlyby the semi-cylindrical forwardly extending walls 210 thereby achievingaccurate axial alignment between the mating optical fibers in theconnector members.

Reference is now made to FIGS. 11 and 12 of the drawings whichillustrate a spring alignment device, generally designated 230, whichmay be employed for axially aligning the optical fibers in a pair ofmating termination pins 44. The device 230 has a generally cylindricalconfiguration and comprises a pair of circular end rings 232 and threelongitudinally extending resilient members 234, each of which is joinedat its opposite ends to the ring members 232 by generally radiallyextending webs 236. The resilient members 234 are offset 120° from eachother and are dimensioned to engage within the indentations 80 of theeyelets 68 on the termination pins 44 when the pins are mounted inopposite ends of the device 230 and abut intermediate the rings 232. Thedevice 230 may be mounted in a cylindrical passage located in the sameplace where a passage 180 is formed in the removable semi-cylindricalplate 160 in the connector illustrated in FIGS. 1 to 10. The springdevice 230 is designed so that when a pair of mating termination pinsextend into opposite ends of the device, the resilient members 234 willbe located between the posts 64 and will exert a radially inwardlydirected spring force on the indentations 80 in the eyelets 68 therebysimultaneously deforming the walls of the eyelets at the indentationsand longitudinally aligning the indentations to achieve axial alignmentof the fiber optic cores in the eyelets. It will be appreciated that thespring device 230 may be inexpensively made by stamping the same from aflat sheet of spring metal and forming the stamped piece into acylindrical configuration. The device 230 is less expensive than thealignment arrangement embodied in the first embodiment of the inventiondisclosed herein, but is incapable of producing as much deformation ofthe indented wall sections of the termination pin eyelets as thepositive camming arrangement of the first embodiment.

It will be appreciated from the foregoing that by the present inventionthere is provided a hermaphroditic fiber optic connector for singleoptical fibers. The connector provides total support for the individualoptical fibers so that the fibers will not break or vibrate when theconnector is used. The connector may be utilized with any form of singleoptical fiber, including optical fiber cores clad with plastic orwithout plastic. If the core is not clad with plastic, preferably theinterstice of the eyelet 68 is filled with a suitable epoxy or cementafter the eyelet has been crimped to completely support the core duringthe polishing of the end face of the termination pin and to mechanicallysupport it against vibration, etc. The connector of the presentinvention has a high mating cycle life. The optical surfaces may bereadily cleaned by removing the semi-cylindrical plates 160 on the endfaces of the support bodies in the connector members. Furthermore, thetermination pins 44 may be readily mounted on optical fibers without therequirement of expensive or complex tools, special processes, or skilledlabor. Thus, the connector is completely field serviceable, therebymaking it particularly suitable for commercial field use.

Most important, the present invention provides a controlled precisealignment of single optical fibers. By way of example only, a connectoras illustrated in FIGS. 1 to 10 may be manufactured which, when utilizedfor coupling a pair of identical 5 mil core plastic clad silica fibers,produces a maximum lateral offset of only 0.2 mils, causing a lighttransmission loss of only 0.1 to 0.3 dB due to lateral misalignment.Considering also light transmission losses resulting from the axial gapbetween the mating end faces of the fibers and Fresnel reflectionlosses, the total light transmission loss between the aforementioned 5mil core fibers in the connector of the present invention would be onlyabout 0.6 dB. Such a loss is indeed minimal for a commerciallypractical, field serviceable connector assembly capable ofinterconnecting a plurality of single optical fibers.

What is claimed is:
 1. A fiber optic connector for coupling opticalfibers comprising:a pair of mating connector members each having a boretherein slidably receiving a termination pin adapted to be connected toan optical fiber, said termination pins being laterally aligned witheach other when said connector members are mated and having mating endfaces; an annular groove in each said termination pin; an annular recessin the wall of each said bore surrounding the groove in the pin in saidbore, said recess providing an annular forwardly facing shoulder; aresilient ring mounted in each said groove and extending outwardly intoits corresponding recess in front of said shoulder; and when saidconnector members are mated, said mating end faces of said pins axiallyabut each other and said forwardly facing shoulders engage said rings toprovide a resilient compression force for contact abutment and relieffor axial manufacturing tolerances.
 2. A fiber optic connector as setforth in claim 1 wherein:each said recess comprises a groove generallyaxially aligned with its corresponding termination pin groove.
 3. Afiber optic connector as set forth in claim 1 wherein:said ringcomprises an elastomeric O-ring.
 4. A fiber optic connector membercomprising:a body having a bore therein slidably receiving a terminationpin adapted to be connected to an optical fiber; an annular groove insaid termination pin, the forward wall of said groove defining arearwardly facing annular shoulder; an annular recess in the wall ofsaid bore surrounding the groove in said pin, said recess providing aforwardly facing annular shoulder; a resilient ring mounted in saidgroove and extending outwardly into said recess in front of saidforwardly facing shoulder; and when said connector member is mated to amating connector, said resilient ring is compressively engaged betweensaid shoulders providing a resilient force tending to resist axialrearward movement of said body in said bore and insuring contactabutment.